A "regressive" (procedure I) and a "progressive" (procedure II) modification of the Papanicolaou stain were tested for their suitability for automated screening procedures. Intermediate squamous cells and carcinoma cells were scanned with a high-resolution system, and digitized data were statistically analyzed after feature extraction. The regressive modification accentuates the textural features of intermediate squamous cell nuclei as well as the contrast ratio of nucleus and cytoplasm. The progressive modification accentuates some criteria of malignancy, such as polychromasia, hyperchromasia and shifting of nuclear to cytoplasmic ratio. Grouping of data according to patients indicates that the differences found are due to the staining procedures and not to individual variability of parameters in different patients.